v0.3.0: structural refactor — go:embed templates, server split, domain rename

- Migrate all 7 HTML templates + CSS from Go string constants to individual
  go:embed files in internal/web/templates/ (templates.go: 2150→35 lines)
- Split server.go into auth.go, handlers.go, funcmap.go (server.go: 540→120 lines)
- Rename controller subdomain from dashboard.* to felhom.* in Traefik labels
- Update documentation (CLAUDE.md, README.md, CONTEXT.md)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/docker-setup.sh

@@ -244,7 +244,7 @@ WHAT THIS SCRIPT INSTALLS:
 
 DEPLOYING APPLICATIONS:
     After infrastructure setup, deploy the felhom-controller to manage apps
-    via the web dashboard at dashboard.<domain>.
+    via the web dashboard at felhom.<domain>.
 
 EXAMPLES:
     # Felhom customer deployment (recommended — full stack with tunnel)
@@ -1473,7 +1473,7 @@ print_summary() {
     echo "  Deploy applications via the Felhom Controller dashboard:"
     echo ""
     echo "  1. Deploy felhom-controller (see controller/README.md)"
-    echo "  2. Open https://dashboard.${BASE_DOMAIN}"
+    echo "  2. Open https://felhom.${BASE_DOMAIN}"
     echo "  3. Browse available apps on the Alkalmazások page"
     echo "  4. Click Telepítés to deploy"
     if [[ -n "$CUSTOMER_ID" ]]; then